Scripting languages are very useful, but my experience is that they're not really designed for enterprise systems and hence don't always handle the mission-critical production financial logic. This is highlighted by the lack of ability to precompile (except in Python) and the lack of standard production services/development features. (Remote debugging, configurable log support, infrastructure for pulling in configuration files, development environments beyond vi, AFAIK.) I did find a prop shop that wrote algorithmic trading scripts in Python and then handed it off to developers to convert into C++; this seems to be more of the exception than the rule, and they were very quick to characterize their work as algorithmic trading first and foremost; not scripting work.There isn't much detail about either job. With information available, I would tend to agree with GoIllini and choose BlackRock for the brand-name.
Furthermore I would stress out that it is useful for anyone to know Perl (or some flavor: PHP, Ruby, Python etc). It offers a clean and flexible language for quick coding. Pattern, matching, hash structures are easy, get results in 5 minutes.
I agree that it doesn't have a solid theoretical foundation, limited OOP, but many times you don't need complete software design. This is especially true if you are in trade support.
And for people that spend more time on it, Perl has significant depth. You can just thing about ~17,000 modules that can be plugged into any code.
Perl is a great language to learn and nearly every group will use it a little, but my (admittedly limited) experience has been that if a group says, "We work almost entirely with perl scripts" and they're not a web development group, they usually don't do a lot of financial development or work with the front office.
At the very least, the emphasis on a scripting language would be a red flag to me if BlackRock is like the bank I work at or the banks some of my friends work at. Since I already had the offer from Credit Suisse, I would be nicely asking BlackRock tough questions like, "So who actually computes the position-specific risk numbers? Do you guys just aggregate numbers from other systems or do you run models yourselves?" "What information comes into your team's system and what information do you guys produce?" "Is it fair to say that your system is just an accounting system? Or does it do more than allocate positiion-level risk to different books?" It would also be good to ask to speak with an existing analyst at both firms and maybe slip in one or two of the same questions.
Questions like these should help give Christian a better idea of what he will be doing at BlackRock. Given all the information I have right now, however, I believe there are better than even odds that the answers will paint the system as aggregating risk feeds and figuring out which book they go under- something that has applications only to a high-school level bookkeeping course.